A.R. MEAD 



with the rich coloration of the mature specimen. Under 

 suitable conditions, both types of individuals are able to 

 assume the basic genital proportions that are typical of the 

 species. In the long term, the shell reflects and responds to 

 the pressures of selection in a changing or in a new environ- 

 ment. Wholly different molluscan stocks moving into distinct 

 but similar environments may evolve convergently into forms 

 that are so similar that conchologically they cannot reason- 

 ably be distinguished or identified without first knowing the 

 locality, e.g. Achatina (Lissachatina) craveni Smith, 1881 and 

 A. (Achatina) tavaresiana Morelet, 1866 (Mead, 1992). 

 Although in the long term, the soft anatomy undergoes 

 changes, it revealingly does so within a more restricted, basic, 

 generalized patten obviously characteristic of the larger 

 group of which it is a related part. At this stage of investiga- 

 tions, these larger groups seem to be taking shape within 

 genera and subgenera (sensu Bequaert, 1950). 



All these factors have so entered into the present project 

 that nine species, once thought to be congeners on the basis 

 of the great similarity in their familial unique shell characters, 

 are now separated into two subfamilies. The shells are 

 remarkably similar, but the soft anatomies convincingly tell a 

 different story. In essence, in the Achatinidae the soft 

 anatomy reveals dependable, differentiating taxonomic crite- 

 ria at the species level and above; the shell usually reveals 

 supporting taxonomic criteria at the species level and often 

 convincing criteria at the subspecies level. A more clear 

 concept of subspecies is beginning to emerge in this family: 

 Essentially consistent, usually minor shell differences in the 

 members of an allopatric population that have features in 

 their soft anatomy indistinguishable from those of the nomi- 

 nate subspecies. This is precisely why the erstwhile enigmatic 

 Leptocala petitia is shown in the text to be a distinct species 

 rather than a subspecies or a synonym of the conchologically 

 very slightly different L. mollicella. 



The shells of the nine species in this project have been 

 redescribed in the light of larger series of specimens and more 

 detailed examinations of shell characters than in previous 

 studies. In many full grown specimens, weathering and 

 environmental abrasion have obscured or removed valuable 

 shell characters, particularly in the upper whorls. The empha- 

 sis on a comparative examination of juvenile specimens in the 

 present study, therefore, has been especially informative. In 

 fact, it strongly supports the value of the collecting juvenile 

 specimens, along with the larger specimens, whenever they 

 are available. For the same reasons, determining the number 

 of whorls is always an imprecise measurement and thus is 

 recorded here only to the nearest one-quarter whorl. The 

 length of the last whorl (= body whorl) includes the entire 

 whorl and is measured from the base of the aperture to the 

 point on the suture immediately above where the outer lip 

 attaches at the periphery. All shell measurements are carried 

 to the nearest 0.1 mm. For many decades the basic horizontal 

 and vertical sculpture of the achatinid shell has been referred 

 to as 'decussate'; this has been changed in the present work to 

 the more accurate term 'cancellate'. From the shell dimen- 

 sions, two important relationships are drawn: 1) between the 

 greatest shell width and the shell length, and 2) between the 

 length of the last whorl and the shell length. These relation- 

 ships are expressed in percentages rather than in ratios. This 

 emphasizes the measurement being compared rather than the 

 measurement to which it is being compared; that is, in 

 making comparisons, it is easier to comprehend that the last 

 whorl is 87% of the shell length, than the fact that the length 



is 1.15 times the length of the last whorl. Aperture width does 

 not include the callus. The descriptive shell terminology is 

 largely based on Cox (1960). 



Diligent searching in 49 museums and personal collections, 

 fortunately brought to light an unexpected fair number of 

 alcohol preserved specimens. The museums with the largest 

 and most varied collections of alcohol preserved achatinid 

 specimens are in Tervuren, Stockholm, Berlin, Bruxelles, 

 Paris, Frankfurt and London. But very valuable specimens 

 have been found in museums where there is relatively limited 

 material. It was through the convictions of Edmond Dart- 

 evelle of the Museum National de l'Afrique Centrale (Ter- 

 vuren) that the wet collection of the museum is unparalleled 

 in quantity and diversity. Because the available material used 

 in the present project is limited, determined efforts were 

 made, after establishing the basic genital pattern, to conserve 

 the remaining specimens for future investigators. 



The relationships of the basal genital system show to 

 greater comparative advantage in ventral view. For this 

 reason, the line drawings are similarly oriented in this per- 

 spective, with the male conduit to the left and the female 

 conduit to the right, unless otherwise indicated. The indi- 

 vidual structures of the conduits are spread apart to show 

 their configuration and minimize obstruction. The drawings 

 are idealized, where possible through multiple specimens, to 

 eliminate irrelevant and misleading features produced in 

 preservation. The origin of the penial retractor is on the male 

 conduit at a point that marks the division between penis and 

 vas deferens. As the retractor anlage reaches apically during 

 development, it usually inserts somewhere on the columellar 

 muscle system, but may insert on the body wall, diaphragm, 

 transverse myoseptum or other sites in the haemocoele 

 (Mead, 1950). The configuration of the developing viscera 

 may predispose the manner of insertion. The not infrequent 

 bifurcate (Fig. 20) and multifurcate penial retractor insertions 

 support the ontogenetic rather than the functional interpreta- 

 tion of these terms. Within a species, the site of insertion may 

 be consistent or variable. There is a fairly strong tendency in 

 this family for the basal penial retractor to proliferate muscle 

 and apparently connective tissue that variously produce adhe- 

 sions in the several parts of the male conduit. This in turn 

 changes the relationship of these parts, alters the extrover- 

 sion process, and the configuration of the resultant intromit- 

 tent organ. This organ is normally composed seriatim, apex 

 to base, of the penis, pilaster (when present), penis sheath, 

 penial atrium and genital atrium externally, and the basal vas 

 deferens, penial retractor, apical vas deferens and ejaculatory 

 duct internally. 



Directions of left and right refer to those of the snail. 

 Apical, in reference to the genital system, means toward the 

 ovotestis, basal toward the genital atrium. The anatomical 

 terminology is essentially that of Mead (1950) (see Abbrevia- 

 tions - Anatomical below). 



The discussion of each species is in the following format: 

 shell, soft anatomy (where available), type material, type 

 locality, distribution and, when applicable, remarks. The 

 sources and localities of the alcohol-preserved specimens are 

 reported in the text. A table for each species includes the 

 sources of all shell specimens examined, taxonomically 

 important specimens, illustrated specimens, a size range, 

 their localities, shell dimensions and shell proportions. Illus- 

 trations in the literature are cited in the synonymies; the 

 nature of the illustration, where it is other than of the shell, is 

 shown in parentheses. Most localities were found in the 





